Mary Babb was in her SUV last year when her estranged husband slammed into her with his pickup truck. The crash overturned Babb's vehicle and left her suspended upside-down by her seat belt.

As she hung there helplessly, Thomas Babb fired two rounds from a shotgun, killing his wife in front of horrified witnesses outside the office where she worked.

Now Mary Babb's family has lobbied successfully for Michigan to join a growing number of states that have expanded electronic monitoring to include domestic abusers and stalkers.

Before her death, the 30-year-old Mary Babb had filed for divorce and moved out of the dwelling she had shared with her husband. She changed jobs and obtained a court order protecting her from her husband. But he kept following her.

"She did everything the law provided her, and it wasn't enough," said Mary Babb's brother, Michael Anderson.

Michigan's new law allows judges to order domestic-violence suspects to wear GPS devices -- even before they go to trial. The idea is to alert victims if alleged abusers are nearby.

That measure joins another law signed this month by Gov. Jennifer Granholm that requires paroled prisoners who have been convicted of aggravated stalking to wear GPS tethers.

GPS devices have been used for years to monitor sex offenders. But technological advances have now made it possible for the systems to issue warnings by cell phone if the offender gets too close to a specific victim.

Massachusetts adopted a law last year that lets judges require electronic monitoring of people who violate personal-protection orders. Michigan, Oklahoma and Hawaii followed suit this year with GPS laws, bringing to 11 the number of states with related measures, said Diane Rosenfeld, a lecturer at Harvard Law School who proposed the Massachusetts law. [Mark Godsey]